1. Field of the Invention
The subject invention is directed generally to fuel delivery systems for gas turbine engines, and more particularly, to a thermally efficient multiple stage fixed displacement gear pump for use in aerospace engine applications.
2. Background of the Related Art
Single stage fixed displacement gear pumps are well known in the art and are often used in low horsepower aerospace applications for delivering fuel to a fuel metering unit of a gas turbine engine. These pumps are used to create pressure through the meshing of gear teeth, which forces fluid around the gears to the outlet side of the pump. In a gear pump, a drive mechanism delivers power to a driving gear. The driving gear then transmits the power to a meshing driven gear to perform work and move fluid through the pump.
Low energy consumption pumping systems are being developed in the aerospace industry as an alternative to traditional single stage fixed displacement gear pumps. One way of doing this is to divide the single pumping stage into multiple pumping stages that can be switched on and off at different operating regimes, depending upon the demand for fluid. These systems improve pump performance by reducing excess heat generated by the pumping gears of a single stage pump. However, each stage typically includes a separate set of gears and bearings, thus increasing the cost and weight of such a pumping system.
Because low cost and weight are critical factors in designing hardware for aerospace applications, it would be beneficial to provide a thermally efficient multiple stage fixed displacement gear pump that utilizes fewer component parts. The pumping system of the subject invention achieves this goal by sharing various mechanical components between pumping stages.